Molecular devices and methods, also referred to as nanoscale devices and methods, or simply as nano-devices and nano-methods, are being widely investigated for present and future generations of electronic devices. Nanoscale devices and methods may employ one or more nanoparticles that are less than about 20 nm in size and, in some embodiments, less than or about 10 nm in size. These nanoparticle-based systems may provide higher integration density than may be available using current microelectronic technology. Moreover, because of their size, nanoscale devices and methods may provide devices and/or methods that have different functionality from conventional microelectronic devices and/or methods. Thus, for example, single electron transistors have been widely investigated for high density and/or high performance microelectronic devices. As is well known to those having skill in the art, single electron transistors use single electron nanoelectronics that can operate based on the flow of single electrons through nanometer-sized particles, also referred to as nanoparticles. In a single electron transistor, transfer of electrons may take place based on the tunneling of single electrons through the nanoparticles. Single electron transistors are described in articles by Brousseau, III et al., entitled pH-Gated Single-Electron Tunneling in Chemically Modified Gold Nanoclusters, Journal of the American Chemical Society, Vol. 120, No. 30, 1998, pp. 7645-7646, and by Feldheim et al., entitled Self-Assembly of Single Electron Transistors and Related Devices, Chemical Society Reviews, Vol. 27, 1998, pp. 1-12.
Another major avenue of investigation in nanotechnology is the assembly of nanoparticles into arrays. See the article by Brousseau, III et al., entitled Assembly of Phenylacetylene-Bridged Gold Nanocluster Dimers and Trimers, Advanced Materials, Vol. 11, No. 6, 1999, pp. 447-449, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. Also see the article by Novak et al., entitled Assembly of Phenylacetylene-Bridged Silver and Gold Nanoparticle Arrays, Journal of the American Chemical Society, Vol. 122, No. 16, 2000, pp. 3979-3980, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein.
As described in the Brousseau, III et al. Advanced Materials article, studies of inorganic clusters continue to reveal fundamental information regarding the size, shape and medium-dependent optical and electronic behaviors of nanoscopic materials. Much of this research has involved characterization of the collective properties of disordered and crystalline two-dimensional (2D) and three-dimensional (3D) arrangements of clusters. Optical absorptions and electron hopping in these crystals of clusters have proven to be strongly dependent on the distance and medium between clusters. These observations have generated interest in nanoclusters on several more applied fronts; e.g., gold cluster chemiresistive sensors and deoxyribonucleic acid assay methods have been reported recently.
As also noted in the Brousseau, III et al. Advanced Materials article, the fundamental and applied advances described above vis-a-vis extended cluster networks prompted examination of the properties of more discrete assemblies of nanoclusters (e.g., dimers, trimers, etc.) so that the effects of local symmetry on collective particle properties could be better assessed. The assembly of phenylacetylene-bridged gold nanoparticle dimers and trimers from solution is reported. Phenylacetylene oligomers I and II (PA I, II) were chosen as basic linker repeat units because: 1) they are conformationally rigid molecules which could be expected to keep coupled nanoparticles at a fixed distance, an important difference from the DNA-linked systems reported previously; 2) they can be coupled to form a variety of geometries (e.g., linear, bent, trigonal planar, tetrahedral); 3) lengths of up to 16 repeat units (ca. 20 nm) are readily synthesized without significant solubility problems; and 4) they have been discussed as potential wire candidates for molecular electronic devices. Given these advantages, the Brousseau, III et al. Advanced Materials article indicated that the successful synthesis of PA-bridged gold nanoparticles would allow particle array symmetry-optical property relationships to be established. Indeed, initial optical studies reported therein found, in accord with theoretical predictions, that array symmetry does influence optical properties.